The present invention relates to a sample loading mechanism and particularly to apparatus for loading small samples into crucibles employed with a furnace for combusting the samples into constitute gases for subsequent analysis.
In furnaces employed for combusting relatively small (1/2 to 1 gram) samples of, for example, steel, typically resistance or induction furnaces are employed. Graphic crucibles are employed for resistance heating of the crucible directly when placed between a pair of electrodes. Ceramic crucibles are typically employed when a specimen is heated by an induction field provided by an activated coil surrounding the crucible. In both combustion furnaces, it is necessary to initially outgas the crucible to assure no contaminate gases are mixed with the specimen gases resulting from the combustion of the sample. With manual loading of crucibles, it is necessary in the prior art systems to open the combustion chamber after the outgasing of the crucible to gain access to the crucible to insert the sample. When doing so, however, the crucible is exposed to atmospheric gases which can contaminate the crucible to an extent that the analytical results can be adversely affected.
In order to prevent the re-exposure of an outgassed crucible to atmospheric conditions, automatic sample loading mechanisms have been attempted. One such attempt includes a sample holding cup formed in a rotatable carrier rod which seals an opening in an upper electrode of a resistance furnace which communicates with the crucible. The rotatable cup including rod, is rotated 180.degree. to in effect dump the sample out and downwardly into the mouth of the crucible. The operation of such a device was not proven to be satisfactory inasmuch as the rotation of the rod tended to throw the sample outwardly from the loading mechanism due to the centrifugal force applied to the sample when the cup was rotated. The result either caused jamming of the rotatable loading mechanism by the specimen or the sample would not be dropped into the crucible.